Thermoelectric generator



Sept 3% 346. w, R RAY THERMOELEGTRIC GENERATOR Filed April 9, 1941 5Sheets-Sheet l INYV E N TO R l V/fl/a I? 0y. SW56) ATTORNEY W. R. RAY

THERMOELECTRIC GENERATOR Sepft. m, @946.

3 Sheets-Sheet 2 Filed April 9, 1941 INVENTOR VV/W/am ERG fiY m ATTORNEY3 Sheets-Sheet 3 C w W N I m M MP w in? w R 25 9 m a a I I l 1 a V NSept. 1@, H9460 R RAY THERMOELECTRIC GENERATOR Filed April 9, 1941Patented Sept. 10, 1946 2,407,517 THERMOELECTRIC GENERATOR William R.Ray, Glendale, Calif., assignor to General Controls 00., a corporationApplication April 9, 1941, Serial No. 387,591

9 Claims.

This invention relates to thermoelectric generators; and particularly togenerators that are adapted to be operated by the heat developed bycombustion of a fuel, as for example, by a gas pilot burner.

Such thermoelectric generator may be used to provide electrical energyfor the controlling functions of a fuel burner control system. Thetheory of operation of such generators is well understood and it isunnecessary to set it forth at length. Conductors made fromthermoelectrically dissimilar metals (such as Chromel and Copel) areconnected in alternate series arrangement; and if alternate junctionsare heated as by a pilot burner flame, there is a consequent creation ofelectrical energy. The heated junctions are the hot junctions; and theunheated junctions are usually termed the cold junctions. The amount ofelectrical energy developed is a function of the temperaturedifferential between the hot and cold junctions.

Suitable temperature differentials may be readily obtained by extendingthe conductor so as to form the cold junctions at a place where theburner flames have no appreciable influence on the temperature. Such anexpedient however requires that quite long conductors be used. Sincethese conductors are made of material having relatively high resistanceand are also quite expensive, it is highly desirous to secure thenecessary temperature differential otherwise than by an extension of theconductors.

In a prior application, Serial No. 299,322, filed October 13, 1939, nowPatent No. 2,340,899, dated February 2, 1944, for Thermocouplestructure," in the name of William R. Ray, there are disclosed severalforms of thermoelectric generators that accomplish these importantresults; particularly by placing the cold junctions inside of the pilotburner tube where the cool stream of unignited fuel serves to absorbheat from the cold junction. This application is a continuation in partof the said prior application.

It is an object of this invention to provide a simple and compactthermoelectric generator of the kind that can be supported within aburner tube.

It is another object of this invention to make it possible to utilize acompact pre-assembled thermoelectric generator structure readilyinsertable into a burner tube; the assembly being such that theelectrical connections are all adequately provided for without danger ofany inadvertent short circuiting.

It is still another object of the invention to provide a compactpre-assembled unit of this character in which is incorporated coolingextensions joined to the cold junctions so as to absorb and transmitheat from the cold junctions. In this way the temperature differentialbetween the hot and cold junctions is materially increased withattendant greater energy generation.

This invention possesses many other advantages, and has other objectswhich may be made more easily apparent from a consideration of severalembodiments of the invention. For this purpose there are shown a fewforms in the drawings accompanying and forming part of the presentspecification. These forms will now be described in detail, illustratingthe general principles of the invention; but it is to be understood thatthis detailed description is not to be taken in a limiting sense, sincethe scope of the invention is best defined by the appended claims.

In the drawings:

Figure 1 is an enlarged longitudinal section of a thermoelectricgenerator incorporating the invention;

Fig. 2 is a view similar to Fig. 1, of a modified form of the invention:

Fig. 3 is a side elevation of the structure illustrated in Fig. 2;

Figs. 4 and 5 are sectional views taken respectively on planes 4-4 and5-5 of Fig. 2;

Fig. 6 is a view similar to Fig. 1 of a further modified form of theinvention;

Figs. 7 and 8 are sectional views taken respec tively along planes 7-1and 8-8 of Fig. 1;

Fig. 9 is a diagrammatic development, showing the thermocoupleconductors utilized in connection with the form of the inventionillustrated in Fig.

Fig. 10 is a view similar to Fig. 1 of a further modified form of theinvention;

Fig. 11 is a view similar to Fig. 1 of a still further modified form ofthe invention; and

Fig, 12 is a diagrammatic development, showing the thermocoupleconductors utilized in connection with the form of the inventionillustrated in Fig. 11.

In general, the thermoelectric generator is so arranged that it may bereadily inserted and supported Within a fuel burner tube, such as apilot burner tube. It is possible to utilize either a single pair ofthermoelectric conductors, or a plurality of pairs of conductors,forming a series of alternate hot and cold junctions.

In the form shown in Fig. 1, a thermocouple employing a single hotjunction is illustrated. In this form of the invention, the thermocoupleconductors I and 2 (of comparatively large cross section) are shown asjoined as by being fused together at their upper ends 3 to form the hotjunction. This hot junction is shown as enveloped by the flame 4 of aburner; and the thermocouple structure is shown as supported within thburner head 5.

The burner head 5 in this form is shown as having a lower threadedextension 6 threaded into the top of a base structure '1. A collar 6'may be provided around head 5 to facilitate turning the head 5 into thethreads of base 1. This base 1 is a downwardly directed tubularextension or branch 8 for conducting a fuel mixture of gas and air tothe open bottom of the head 5. This mixture is formed by the aid of theincoming gas passing through the nozzle aperture 3 and past the airinlet apertures l3, formed within a coupling member ii. ne end of thismember ii is threaded into the end of branch 8; and the other end isadapted to accommodate an appropriate conduit leading from a source offuel.

In the present instance the thermocouple conductors I and 2 are shown asenveloped by a metal jacket l2, as of stainless steel. posed hotjunction 3 may be fused to the top of this jacket l2, so that there is adefinite connection between the jacliet l2 and the conductors. A layerof insulation 53, such as thin mica, may be interposed between thethermocouple conductors I and Similarly a mica tube i4 may be insertedwithin the jacket i2 and may surround the thermocouple conductors I and2-, to ensure against any short circuiting oi the conductors below thehot junction. The fuel mixture thus passes through an annular passage I5formed between jacket I2 and head 5.

The lower ends of the thermocouple conductors are shown as fused orotherwise attached respectively to the twin conductors or leads i6 andI1 of armored cabi'e i3. These joints form the cold junctions I5 and I1.This armored cable l-S is shown as extending through the thin metalsleeve i9, which may be of brass. brazed to the bottom of the jacket I2.The metallic sheath of cable 13 may be joined as by welding, solderingor brazing, to the interior of the tube E9. The cold junctions are shownin this instance as encompassed within the tube or sleeve 59. This tubeis cooled by the cold fuel stream and there is transfer of heat from thecold junctions through this tube and into the fuel stream.

The tubular member I!) is arranged to pass downwardly through the base iand past the apertured flange 2 3 located within th base 1. The tube I3fits snugly within this aperture, to aid in rendering the structure airtight. The tube Ii] also passes beyond the lower extremity of a threadedaperture 2-1, in the bottom of base 1. This threaded aperture isprovided for the accommodation of a hollow threaded sealing plug 22which fits snugly around the tube Hi. The inner extremity of the plug 22is arranged to engage a tapered collar 23 disposed around the tube l3and made of deformable material, to form a seal around the tube. Theupper edge of the collar '23 iits against the lower surface of theflange 25,

In this formof the invention, the cool mixture of fuel and air passesthrough the extension 8 into the head 5, and past the metal sheath 2.The cold junctions l5 and I1 transmit heat to the tube E9, which iscooled by the passage of the stream of fuel mixture around the sheathi2.

The pilot burner tube structure of Fig. l illus- The extrates but oneform that such a structure may take. It may be formed relativelyinexpensively by the aid of sheet metal parts that may be joinedtogether by welding. Such an arrangement is illustrated in Figs. 2, 3, 4and 5.

In this form there are provided casing halves or shells 24 and 25. Thesehalves are shown as being provided with contacting flanges 26, 21 and23, 29 (see particularly Figs. 4 and 5). By the aid of these flanges thehalves may be joined together as by stitch welding, indicated in generalby the dotted lines '33 of Fig. 2.

The right hand portions of the casing 24 and have depressions orchannels defining a tubular passageway 3| extending entirely through thestructure. This passageway 3| has an upper enlarged portion 32. Locatedwithin the passageway 3| is the metallic sheath 33 of a thermoelectricgenerator structure. This sheath is shown as capped by a metal capmember 34 extending upwardly beyond the enlarged portion 32 of theburner tube. The leads 35 and 36 for the thermocouple structure extend,into the sheath 33. Both the sheath '33 and the cap 34 are prefarablymade from non-corrosive material such as stainless steel. The cap 34furthermore encloses the hot thermocouple junctions.

The cap 34 is arranged to be heated by a flame 31 (Fig. 2). Fuel forthis flames is provided by the aid of a plurality of jet passageways 38formed by the aid of slots in the top flange of the tubular portion 3|.These slots together with the exterior cylindrical surface of the cap 34form a series of jet apertures through which a combustible mixture maypass to form the flame 31. This flame 31 encompasses the cap 34 andheats it for raising the temperature of the hot junctions enclosedwithin this cap 34. The slots 38 may be uniformly spaced about theburner, for example as illustrated by slots 1| of Fig. '7.

The fuel mixture is passed into the enlarged portion 32 from the branchpassageway 39 formed by channels or depressions in the casing shells 24,25. This branch passageway further communicates as through a restrictedopening 40. with a chamber 4|. This chamber 4| is in communication withthe air as by the aid of one or more radial apertures 42. The chamber 4|which forms the mixing chamber is also in communication with a source ofgaseous fuel. This is accomplished by the aid of a nozzle opening 43'formed in a coupling member 44. This coupling member 44 has acylindrical upper portion 45 tele's-cop'ed within the tubular passage 46formed in the casing 24-25. It is also provided with an appropriateinternally threaded extension 41 by the aid of which a fuel conduit maybe attached to the coupling member 44. This extension 41 is shown ashaving an external hexagonal surface. As shown most clearly in Fig. 2,the upper end of the coupling member 44 may be tapered to a seat againstthe shoulder 48 formed beneath the mixing chamber 4 I.

The fuel passes upwardly through the coupling member 44 and through thenozzle opening 43 into the mixing chamber 4|. Air is drawn in throughapertures 42 into this mixing chamber and the combustible mixture thenpasses upwardly into the passageway 39 and thence the fuel mixtureproceeds upwardly around the upper portion of the sheath 43 into theenlarged portion '32 of the tubular structure 3|. The fuel finallypasses through the jet openings 38 and burns as indicated by the flame31.

Provisions are made to ensure against leakage'of fuel past the sheath 33or downwardly past the coupling member 44. For this purpose the couplingmember 44 and the sheath 33 are quite tightly enclosed within the wallsof the casing shells 24 and 25. In addition, a clamping arrangement maybe provided adjacent the lower end of the structure. This may take theform of a pair of strap members 49, 50 (Figs. 3 and 4) These strapmember are appropriately curved to encompass the external cylindricalsurfaces of the casing members 24, 25. They are urged into clampingposition as by the aid of a screw passing through the members 49-50, aswell as between the tubular portions 46 and 31 of the casing member.

The flame 31 is utilized primarily for supplying heat to thethermoelectric generator. The burner may also be utilized as a pilotburner as by providing an aperture 52 communicating with the upperenlarged portion 32 of the tube 3|. The pilot flame 53 is shown asissuing therefrom.

' Furthermore, in order to provide a convenient supporting means for thecomplete thermoelectric generator structure, the casing halves 24 andmay be extended at the left hand side to form the contacting flatportions 54 and 55 (Figs. 2 and 5). These contacting portions may bewelded together and may be provided with one or more apertures 56. Bythe aid of these apertures the structure may be appropriately fastenedto a stationary support.

The thermoelectric generator enclosed within the sheath 33 of the cap 34may take any of several forms. These forms will be described hereinafterin connection with other modifications of the burner tube structure. 7In the modification illustrated in Figs. 6, 7, 8 and 9, a burner tube 51is shown having an integrally formed fuel mixture conduit 58. Thisburner tube 51 is open at the top and bottom. It has an intermediateflange 59 through which the sheath 60 of the thermoelectric generatorpasses. This sheath 60 extends completely through the tube 51. It isheld in fluid tight sealed relation with respect to the flange 59 as bythe aid of the metal packing ring 6|. This may be made of deformablematerial to form a tight seal around the exterior of the sheath 60. Thedeformation may be accomplished by the aid of a hollow threaded sealingplug 62.

The deformable collar 6| has an internal cylindrical surface closelycontacting the sheath 60 and is urged against the sheath 60 by thecooperation of the tapering contacting surface of the threaded plug 62and the collar 6|.

The fuel mixture supplied through the conduit 58 is passed into theannular space 63 around the sheath 6!]. The fuel is passed into theconduit 58 through the nozzle member 64 located in the couplingextension 65 of the conduit 53. Radial air apertures 66 extend into theconduit 58. for forming the fuel mixture.

The sheath 68 telescopes within the depending skirt portion 61 of ametal cap 68. This metal cap 68 encloses the hot junctions of thethermoelectric generator constructed in a manner to be hereinafterdescribed.

The upper end of the tubular member 51 is threaded for the accommodationof a hollow jet forming metallic member 69. This metallic memberhasian'upper flange v1t through which the joined in series relation.

, tory support 15.

cap 68 extends. This flange as shown most clearly in Fig. 7 may beprovided with a series of radial slots 1| to form jet openings incooperation with the external cylindrical surface of the cap 68. Aburner flame '12 issues from these jet openings 1| and encompasses andheats the cap 68.

The flame 12 is used primarily to provide heat for the generation ofelectrical energy. A pilot flame 13 may be provided for and may issuefrom an aperture 14 formed in the hollow metallic member 69. e

A refractory insulation member'15 serves as a support for thethermoelectric conductors and is shown as telescoping within the top ofthe sheath 60. This insulation member 15 (which may conveniently be madeof porcelain) has an enlarged head to form a shoulder against which thetop end of thetubular sheath 60 may abut. Similarly, the upper surfaceof the insulation member 15 is in contact with the shoulder of cap 68formed between the skirt 61 of the cap and the upper portion of the cap.In this way upon proper fusion of the cap 63 into the sheath 60, theinsulation support 15 is firmly secured in place near the top of themetal casing.

A space 16 is enclosed by the cap 68 in con-; junction with the topsurface of the support 15. The pairs of thermoelectric conductors 11-18,etc., pass through apertures in the support 15. One series of conductors11 form an outer annular arrangement, around the other series ofconductors 18 which form an inner annular arrangement. The pairs ofconductors 1113 ar joined together to form a twisted connectionillustrated at 19 (Figs. 6 and 9). These twisted ends form the hotjunctions. Heat is sup: plied to them by radiation from the heated cap68.

In the present instance the cold junctions are formed beneath thesupport 15 as by joining the alternate conductors as indicated by thetwisted wires 88. Conductors 11 and 18 may be respec-, tively of Chromeland Copel. As shown most clearly in Fig. 9, the thermocouples are thusThe end conductors may be connected as by the copper leads 8| and 82 toa load 83. This load 83 may be an electromagnet or a relay or the like,as for controlling the supply of fuel to a main burner, or the generatedelectricity may be utilized for any other desired controlling function.

The hot junctions 19 being supported above the refractory support 15 donot materially afiect the cold junctions 88 disposed below the refrac-Furthermore, due to the flow of the cool fuel mixture past the sheath 60the transfer of heat to the cold junctions is very materially retarded.Although the thermoelectric conductors 11 and 18 are quite short, thetemperature differential between the hot and cold junctions is ample toprovide the desired electrical energy.

However, in order further to ensure that the cold junctions 88 will bemaintained at a proper low temperature, heat dissipating or radiatingmetal extensions 84 may be joined to the cold junctions 88. Theseextensions may be of copper wire. They serve to transfer heat from thecold junctions to the circumambient atmosphere that,

is in communication with the lower end of the sheath 60. The ends ofthese heat radiators 84 may be conveniently disposed around a refractoryor insulation ring 85. This ring 85 is telescoped over the lower end ofthe sheath 60. It may be provided with a plurality of notches 86 asillustrated in Fig. 8. The extensions 84 pass downwardly and out of the openend-of the sheath 60. They may then be turned upwardly to beaccommodated within the notches 86. The ring 85 may be held in placeagainst axial movement on the sheath 69 as by the aid of the upsetportion 81 formed on the sheath 6e and the out- Zvardly turned flange 88at the end of the sheath The interior of the sheath 89 being hollow andin communication with the outside the cooling of the cold junctions 89is rendered very effective. The radiating surfaces of the heatconductors 84 being exposed to the external air also assist to maintain.the temperature of the cold junctions at a suitable low value- It is notalways essential to utilize th heat radiating elements 84. In the formof the invention illustrated in Fig. 10 these conductors are omitted; aswell as the ring 85. The sheath 89 in this case simply extendsdownwardly past the hollow threaded clamping member 52. Thecoldjunctions 89 and the hot junctions (9 are arranged as before.

In the form of the invention illustrated in Figs 11 and 12, the coolingeffect of the cold junctions is secured otherwise than by the aid of anysupplemental radiating conductors. In this case the pairs ofthermoelectric conductors are designated by the reference characters 90and 91 extending through the refractory insulation support 15. Theconductors 90 may be made of Copel, and extend for a considerabledistance beyond the sheath 89. The conductors 9|, however, are short andmay be made of Chromel. These conductors are within the support 15 andmay be joined as by copper leads 92 to form the cold junctions 93. Byusing these copper leads 92 as extensions of the Chromel conductors, theresistance of these Chromel conductors is kept within reasonable limits.Since the resistance of Chromel is quite high, the'shortening of theChromel conductors thus rendered possible is quite important.

Since the thermoelectric characteristics of some types of Chromel andcopper are somewhat similar, the joints I03] between the conductors 92and the Chromel conductors 9! have little effect upon the generation ofelectricity. The true cold junc tions are formed between copper leads 92and the Copel leads 99. In order to ensure effective cooling of thesecold junctionsthey may be disposed in a braided fashion illustrated ingeneral by the reference character 94 within and beyond the sheath 89.In order to prevent inadvertently short circuiting of any element of thethermoelectric generator, the conductors 90 and leads 92 may be coveredprior to the braiding operation with a thin layer of insulation, such asan enamel layer.

The thermocouple conductors being arranged in series, one of the Copelconductors 99 may form a terminal for the generator. A copper lead 95may be connected to the end of this terminal conductor. The otherterminal conductor is formed by the end copper conductor 92. These leadsmay be covered with appropriate insulation, such as indicated by thebraided sleeves 96 and 97.

As in the forms disclosed in Figs. 6 and 10, the interior of the sheath89 is open to the atmosphere. It is also subjected to the flow of'thecool fuel mixture passing through the conduit 58. Accordingly the coldjunctions are maintained at a suitably low temperature.

What is claimed is:

1. In combination, a burner tube having open ends, a thermoelectricgenerator structure having an external sheath and disposed in said tubeso that one end of the sheath extends beyond the tube and defines withsaid end, one or more burner jets arranged around said extending end, anannular clamping ring disposed around the sheath adjacent the other endof said tube, and in contact with the tube, to close the space betweenthe interior of the tube and the exterior of the sheath, and therebyserving to seal and support said sheath within the tube, and means forpassing a fuel mixture into the tube.-

2. In combination, a burner structure having a fuel jet burner head aswell as an extension for conducting a stream of a mixture of fuel andair to the base of said burner head, a thermocouple structure supportedin the burner head and extending past the base, said thermocouplestructure including a pair of conductors of dissimilar metals forming ahot junction exposed in the name beyond the burner head, saidthermocouple structure, also including a metallic sheath disposed aroundsaid conductors, and clamping means, surrounding said metallic sheath,supported within the burner structure, and operable from the exterior ofsaid burner structure closing the space between the burner head and thesheath, and compressible to grip said sheath.

3. In combination, a pair of sheet metal shells having contactingflanges by the aid of which they may be joined, said shells havingrecesses forming a burner tube as well as a passage for a fuel mixtureinto the tube, said flanges having an extended area at a place to form aconvenient means for fastening the assembled shells to a support, saidburner tube thus formed having open ends, said shells having provisionsfor accommodating an end of a fuel supply conduit in operative relationto said passage. and a thermoelectric generator structure having anexternal sheath extending through the tube, and defining with one end ofthe tube, one or more burner jet openings.

' 4. In combination, a burner tube having open ends, a thermoelectricgenerator structure extending in said tube, comprising an insulationsupport, thermoelectric conductors passing through the support, formingon one side of the support, one or more hot junctions, a metal capdefining with said support a space enclosing the hot junctions, said capbeing within the influence of the burner flame, and a tubular metallicmember carried by said cap to form a sheath, and extending on the otherside of said support leads for the thermoelectric generator structureextending into the tubular member; and means surrounding said tubularmember for supporting said tubular member in fluid tight manner in theburner tube, and sealing one end of said tube,

5. In combination, a burner tube having open ends, a thermoelectricgenerator structure extending in said tube, comprising an insulationsupport, thermoelectric conductors passing through the support, formingon one side of the support, one or more hot junctions, and forming onthe other side of the support, one or more cold junctions, and a metalsheath structure enclosing the hot and cold junctions, and extendinginto the burner tube; and means surrounding said sheath structure forsupporting said sheath structure in fluid tight manner in the burnertube, and sealing one end of said tube.

6, In combination, a burner tube having open ends, a thermoelectricgenerator structure extending in said tube, comprising a metallic sheathstructure, thermoelectric conductors Within said sheath structure andforming one or more hot and cold junctions, heat conducting extensionsjoined respectively to at least some of the cold junctions and extendingout of that end of the sheath structure remote from the hot junctionend, and means co-operating with the said structure for sealing one endof the tube.

7. In combination, a burner tube having open ends, a thermoelectricgenerator structure extending in said tube, comprising a metallic sheathstructure, thermoelectric conductors within said sheath structure andforming one or more hot and cold junctions, heat conducting extensionsjoined respectively to at least some of the cold junctions and extendingout of that end of the sheath structure remote from the hot junctionend, an insulation ring carried by said end of the sheath structure andon which ring said extensions are looped, and means co-operating withthe said structure for sealing one end of the tube.

8. In combination, a burner tube having open ends, a thermoelectricgenerator structure extending in said tube, comprising a metallic sheathstructure, thermoelectric conductors Within said sheath structure andforming one or more hot and cold junctions, an insulation supportthrough which the conductors pass, and Within said sheath structure,those parts of said conductors extending on that side of the supportwhere the cold junctions are formed, being elongated and mechanicallyintertwined, and means co-operating with the said structure for sealingone end of the tube.

9. In a thermoelectric generator structure, an insulation support,thermoelectric conductors passing through the support, forming on oneside of the support, one or more hot junctions, and forming on the otherside of the support one or more cold junctions, a metal cap definingwith said support, an enclosure for said hot junctions, and a tubularmetallic member surrounding said support and cooperating with said capto form an elongated sheath, heat conducting extensions connectedrespectively to at least some of the cold junctions and located withinthe sheath, and an insulation ring carried by the end of the sheath, andaround which ring said extensions are looped.

WILLIAM R. RAY.

